perfidy

noun3

1. •
   A state or act of violating faith or allegiance; violation of a promise or vow, or of trust.
2. •
   An illegitimate act of deception, such as using symbols like the Red Cross or white flag in a false claim of surrender to gain proximity to an enemy for purposes of attack.

   • Stratagems must be carefully distinguished strategy from perfidy, since the former are allowed, whereas the latter is prohibited. — 1921
3. •
   A state or act of deceit.

   • Honda Motor Co. is the latest victim of e-mail perfidy, which started when a phony chain letter promised that the automaker would give away free cars. — 2000